From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Date: Fri, 14 Apr 2017 21:37:59 +1000 Message-ID: <1492169879.25766.4.camel@kernel.crashing.org> References: <1490911959-5146-1-git-send-email-logang@deltatee.com> <1491974532.7236.43.camel@kernel.crashing.org> <5ac22496-56ec-025d-f153-140001d2a7f9@deltatee.com> <1492034124.7236.77.camel@kernel.crashing.org> <81888a1e-eb0d-cbbc-dc66-0a09c32e4ea2@deltatee.com> <20170413232631.GB24910@bhelgaas-glaptop.roam.corp.google.com> <20170414041656.GA30694@obsidianresearch.com> <08c32f0d-6c7c-b65f-6453-dde0d7c173d1@deltatee.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <08c32f0d-6c7c-b65f-6453-dde0d7c173d1-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: Logan Gunthorpe , Jason Gunthorpe , Bjorn Helgaas Cc: Jens Axboe , "James E.J. Bottomley" , "Martin K. Petersen" , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Steve Wise , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Keith Busch , Jerome Glisse , linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org, Max Gurtovoy , Christoph Hellwig List-Id: linux-rdma@vger.kernel.org On Thu, 2017-04-13 at 22:40 -0600, Logan Gunthorpe wrote: > > On 13/04/17 10:16 PM, Jason Gunthorpe wrote: > > I'd suggest just detecting if there is any translation in bus > > addresses anywhere and just hard disabling P2P on such systems. > > That's a fantastic suggestion. It simplifies things significantly. > Unless there are any significant objections I think I will plan on > doing > that. I object. > > On modern hardware with 64 bit BARs there is very little reason to > > have translation, so I think this is a legacy feature. > > Yes, p2pmem users are likely to be designing systems around it (ie > JBOFs) and not trying to shoehorn it onto legacy architectures. > > At the very least, it makes sense to leave it out and if someone > comes > along who cares they can put in the effort to support the address > translation. > > Thanks, > > Logan